Possible factors illuminating increased disparities in neonatal mortality in Wisconsin from 1991-2005.

BACKGROUND Neonatal mortality has been perceived as one of the critical and sensitive measures that reflect not only the heath status of infants and their mothers, but also the general well-being of a society. However, our knowledge of racial disparities in neonatal mortality associated with low birth weight and short gestation is relatively limited. As part of continuing statewide efforts to achieve better birth outcomes, this study intends to develop a better understanding of potential mechanisms contributing to the discrepancy in neonatal mortality rates (NMR) to help public health practitioners formulate more effective interventions to prevent unnecessary infant deaths. OBJECTIVES To assess racial/ethnic disparities in neonatal morality risks by infant birth weight and gestational age in Wisconsin from 1991 through 2005, and to provide more information for programs emphasizing the development of policies and environmental changes to reduce and prevent infant mortality in minority populations. METHODS Linked birth/infant death data were obtained from the Wisconsin Interactive Statistics on Health (WISH) query system by birthweight, prematurity, race/ethnicity for the periods, 1991-1995, 1996-2000, and 2001-2006. The probability of neonatal mortality was analyzed through log-linear Poisson regression models to test for the pattern of variation of neonatal mortality risks in relation to infant's race/ethnicity, birth weight, prematurity, and their interactions. RESULTS The proportion of the neonatal deaths to the infant deaths has gradually increased over time, and accounted for more than two-thirds of Wisconsin infant deaths. Despite a large decrease in white NMRs, neonatal mortality risks for blacks and Hispanics did not significantly change. This discord led to a widened racial/ethnic gap in NMRs. Substantial variations on neonatal mortality risks by birth weight and preterm birth were found among whites, blacks, and Hispanics infants. Notably, among low birth weight and preterm infants, blacks and Hispanics appeared to have more favorable NMRs than whites. White infants had the lowest NMRs only delivered at full-term and about 2500 g. CONCLUSION Wisconsin infant mortality rates are largely driven by neonatal deaths. This shows an urgent need to develop effective public health interventions to prevent early neonatal deaths. To reduce racial/ethnic disparities in NMRs, the design of the interventions should also take into account the variation of the effects of birth weight and gestation age on neonatal mortality among racial/ethnic groups. It is hoped the result of this study will provide a critical understanding: when it comes to racial/ethnic disparities, there is far more to low birth weight or short gestational age than simply not having enough weight or days.